Role of macrophage cell surface sulphydryl groups in endocytosis, but not recognition of immune complexes.

Mononuclear phagocytes play a central role in the removal of immune complexes from the circulation. Cell surface receptors for the Fc domain of IgG mediate, at least in part, the recognition and internalization of particulate and soluble immune complexes. Recently, there have been significant advances in understanding the structural and functional aspects of Fc receptors (Leslie & Alexander, 1979; Zuckerman & Douglas, 1979). However, the post-receptor binding events which trigger endocytosis of immune complexes are not well understood. In the present communication, we employ the membrane-impermeable reagent 5,5′-dithiobis (nitrobenzoic acid), DTNB, to demonstrate that cell surface sulphydryl groups are required for the endocytosis, but not recognition of immune complexes.